A Meldrum's acid-based covalent-assembly fluorescent probe for rapid and sensitive hydrogen sulfide detection.

Hydrogen sulfide (H2S) is an endogenous gaseous signaling molecule involved in various physiological regulatory functions and pathological processes. Therefore, the development of reliable methods for sensitive and selective H2S detection is highly desirable. In this study, a novel Meldrum's acid-based covalent-assembly fluorescent probe, CA-H2S, was developed for the rapid and highly sensitive detection of H2S. CA-H2S employs a 2,4-dinitrophenyl (DNP) moiety as the recognition unit. Upon reaction with H2S, the DNP group is cleaved through nucleophilic aromatic substitution, triggering intramolecular cyclization and rearrangement to generate a highly emissive coumarin fluorophore in situ. CA-H2S produced an approximately 250-fold increase in fluorescence intensity in the presence of H2S and exhibited a high quantum yield of 94%, fast response characteristics, outstanding selectivity, and an ultralow detection limit of 12 nM. Moreover, the probe enabled effective fluorescence imaging of H2S in living cells and mice, suggesting its promising applicability in biological imaging studies.